Organic EL display device

ABSTRACT

An organic EL display device including a substrate, a transparent electrode, a luminescent layer, and a metal electrode layer in this order from a light emission side, a circularly polarizing plate disposed on the light emission side of the substrate, the circularly polarizing plate including a polarizing film and phase difference films that stacked on each other. The phase difference film includes a resin composition (A) containing polystyrene-based polymer having a syndiotactic structure and polyarylene ether, a ratio of the polystyrene-based polymer having the syndiotactic structure with respect to the polyarylene ether in the resin composition (A) is 65:35 to 55:45, being a weight ratio of (the polystyrene-based polymer having the syndiotactic structure) with respect to (the polyarylene ether), the phase difference film satisfies a relation Re 450 &lt;Re 550 &lt;Re 650 , and an Nz coefficient of the phase difference film at a wavelength of 550 nm is −0.25 to −0.05.

FIELD

The present invention relates to an organic EL display device. Morespecifically, the present invention relates to an organic EL displaydevice that includes a circularly polarizing plate formed by stacking apolarizing film and a phase difference film and has good viewing anglecharacteristics and a high anti-reflection effect.

BACKGROUND

A display device using an organic EL luminescent element has a metalelectrode disposed on the rear side of a luminescent layer with respectto an observer. This display device has a problem in that, when externallight is present, its display quality is significantly impaired by lightreflected at the metal electrode or by reflection of a scenery on theobserver side. There is known a technique wherein, for the purpose ofpreventing reflection from the metal, a circularly polarizing plateserving as an anti-reflection film is used on a front substrate of theluminescent element. The circularly polarizing plate includes apolarizing plate and a phase difference film serving as a ¼ wave plate.There is known a technique wherein an oriented polymer film obtained bystretching a polymer film is used as the phase difference film.

When such a prior-art phase difference film is used as a circularlypolarizing film, a favorable anti-reflection effect is obtained only ata certain wavelength at which phase difference is ¼ of the wavelength.However, a favorable anti-reflection effect cannot be obtained over awide wavelength range such as the visible range of 400 nm to 700 nm. Asa result, there occurs a problem of coloration of the reflected light.

Patent Literature 1 discloses that, when an anti-reflection film inwhich phase differences at wavelengths of 450 nm and 550 nm satisfy therelation |R(450)|<|R(550)| (where |R(450)| and |R(550)| represent theabsolute values (nm) of in-plane phase differences at wavelengths of 450nm and 550 nm) is used as a phase difference film, light reflection froma highly reflective reflection surface, such as a metal electrodeincorporated in an electroluminescent display element, can beeffectively prevented over a wide wavelength range.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Laid-Open No.    2001-249222 A

SUMMARY Technical Problem

However, when the anti-reflection film disclosed in Patent Literature 1is used for an organic EL element, viewing angle characteristics may beinsufficient, and contrast of the screen when viewed in an obliquedirection may be insufficient. Further, in some cases, the flexibilityof the film is insufficient, and the film is ruptured in its productionprocess.

The present invention has been created in view of the foregoingproblems, and it is an object to provide an organic EL display devicehaving good viewing angle characteristics and a high anti-reflectioneffect.

Solution to Problem

The present inventor has conducted extensive studies to solve theaforementioned problems and found out that the aforementioned problemscan be solved by employing a circularly polarizing plate produced bystacking a polarizing film and a phase difference film, wherein thephase difference film is a film that is formed from a resin composition(A) containing a polystyrene-based polymer having a syndiotacticstructure and polyarylene ether and has in-plane direction retardationswithin a specific range and an Nz coefficient at a wavelength of 550 nmwithin a specific range. Thus, the present invention has been completed.

The present invention provides the following (1) to (12).

(1) An organic EL display device comprising a substrate, a transparentelectrode, a luminescent layer, and a metal electrode layer in thisorder from a light emission side,

-   -   the organic EL display device further comprising a circularly        polarizing plate disposed on the light emission side of the        substrate, the circularly polarizing plate including a        polarizing film and a phase difference film that are stacked on        each other, wherein    -   the phase difference film includes a layer formed of a resin        composition (A) containing a polystyrene-based polymer having a        syndiotactic structure and polyarylene ether,    -   a ratio of the polystyrene-based polymer having the syndiotactic        structure with respect to the polyarylene ether in the resin        composition (A) is 65:35 to 55:45, the ratio being a weight        ratio of (the polystyrene-based polymer having the syndiotactic        structure) with respect to (the polyarylene ether),    -   the phase difference film satisfies a relation        Re₄₅₀<Re₅₅₀<Re₆₅₀, and    -   an Nz coefficient of the phase difference film at a wavelength        of 550 nm is −0.25 to −0.05        (wherein Re₄₅₀, Re₅₅₀, and Re₆₅₀ are in-plane direction        retardations of the phase difference film at measurement        wavelengths of 450 nm, 550 nm, and 650 nm, respectively,    -   the Nz coefficient represents (nx−nz)/(nx−ny),    -   nx represents a refractive index in a direction of an in-plane        slow axis of the phase difference film,    -   ny represents a refractive index in a direction of an in-plane        fast axis of the phase difference film, and    -   nz represents a refractive index in a thickness direction of the        phase difference film).        (2) The organic EL display device according to (1), wherein        Re₄₅₀/Re₅₅₀ in the phase difference film is 0.80 or more and        0.90 or less.        (3) The organic EL display device according to (1) or (2),        wherein a birefringence Δn (Δn=nx−ny) of the phase difference        film at a wavelength of 550 nm is 0.0020 or more and 0.0050 or        less.        (4) The organic EL display device according to any one of (1) to        (3), wherein the phase difference film has a thickness of 80 μm        or less.        (5) The organic EL display device according to any one of (1) to        (4), wherein the polyarylene ether contains a polymer including        a phenylene ether unit.        (6) The organic EL display device according to any one of (1) to        (5), wherein the in-plane direction retardation Re₅₅₀ of the        phase difference film at a measurement wavelength of 550 nm is        110 nm to 150 nm.        (7) The organic EL display device according to any one of (1) to        (6), wherein the phase difference film is prepared by subjecting        a long-length pre-stretch film formed of the resin        composition (A) to stretching in a direction within a range of        40° or more and 50° or less with respect to a lengthwise        direction of the long-length pre-stretch film.        (8) The organic EL display device according to any one of (1) to        (6), wherein the phase difference film is prepared by subjecting        a long-length pre-stretch film layered body to stretching in a        direction within a range of 40° or more and 50° or less with        respect to a lengthwise direction of the long-length pre-stretch        film layered body, the pre-stretch film layered body including a        P1 layer formed of the resin composition (A) and a P2 layer        provided in contact with the P1 layer and formed of a        thermoplastic resin (B).        (9) The organic EL display device according to any one of (1) to        (6), wherein the phase difference film is prepared by:        subjecting a long-length pre-stretch film layered body to        stretching in a direction within a range of 40° or more and 50°        or less with respect to a lengthwise direction of the        long-length pre-stretch film layered body, the pre-stretch film        layered body including a P1 layer formed of the resin        composition (A) and a P2 layer provided in contact with the P1        layer and formed of a thermoplastic resin (B), whereby a phase        difference film layered body including a p1 layer formed by        stretching the P1 layer and a p2 layer formed by stretching the        P2 layer is obtained; and then removing the p2 layer.        (10) The organic EL display device according to (8) or (9),        wherein the thermoplastic resin (B) is at least one selected        from acrylic resins, resins containing alicyclic        structure-containing polymers, and polycarbonate resins.        (11) The organic EL display device according to any one of (8)        to (10), wherein the long-length pre-stretch film layered body        is obtained by co-extrusion or co-flow casting of the resin        composition (A) and the thermoplastic resin (B).        (12) The organic EL display device according to any one of (7)        to (11), wherein the stretching is performed at a temperature        equal to or higher than (Tg−15)° C. and equal to or lower than        (Tg+1)° C., wherein (Tg) is the glass transition temperature of        the resin composition (A).

Advantageous Effects of Invention

According to the present invention, an organic EL display device havinggood viewing angle characteristics and a high anti-reflection effect canbe obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a contrast map of an organic EL display device obtained inExample 1.

FIG. 2 is a color tone map of the organic EL display device obtained inExample 1.

FIG. 3 is a contrast map of an organic EL display device obtained inExample 2.

FIG. 4 is a color tone map of the organic EL display device obtained inExample 2.

FIG. 5 is a contrast map of an organic EL display device obtained inExample 3.

FIG. 6 is a color tone map of the organic EL display device obtained inExample 3.

FIG. 7 is a contrast map of an organic EL display device obtained inComparative Example 1.

FIG. 8 is a color tone map of the organic EL display device obtained inComparative Example 1.

FIG. 9 is a contrast map of an organic EL display device obtained inComparative Example 2.

FIG. 10 is a color tone map of the organic EL display device obtained inComparative Example 2.

FIG. 11 is a contrast map of an organic EL display device obtained inComparative Example 4.

FIG. 12 is a color tone map of the organic EL display device obtained inComparative Example 4.

DESCRIPTION OF EMBODIMENTS

The present invention will be described in detail by way of embodimentsand exemplifications. However, the present invention is not limited tothe following embodiments and exemplifications and may be implementedwith any modifications without departing from the scope of the claims ofthe present invention and equivalents thereto.

In the following description, “(meth)acrylic” is meant to include bothacrylic and methacrylic.

The organic EL display device of the present invention includes asubstrate, a transparent electrode, a luminescent layer, and a metalelectrode layer in this order from a light-emitting side, and furtherincludes a circularly polarizing plate formed by stacking a polarizingfilm and a phase difference film on the light-emitting side of thesubstrate.

(Resin Composition (A))

The phase difference film includes a layer formed of a resin composition(A) containing a polystyrene-based polymer having a syndiotacticstructure and polyarylene ether. The polystyrene-based polymer having asyndiotactic structure means that the stereochemical structure of thepolystyrene-based polymer is a syndiotactic structure. The syndiotacticstructure is a stereo structure in which, in a Fischer projectionformula, phenyl groups, which are side chains, are located alternatelyon opposite sides with respect to the main chain formed fromcarbon-carbon bonds.

The tacticity (stereoregularity) of the polystyrene-based polymer may bequantified by a nuclear magnetic resonance method using a carbon isotope(¹³C-NMR method). The tacticity measured by the ¹³C-NMR method may berepresented by the existence ratio of constituent units that aresuccessively present in plurality. Generally, e.g., two successivestructural units constitute a dyad, three successive structural unitsconstitute a triad, and five successive structural units constitute apentad. In this case, the polystyrene-based polymer having asyndiotactic structure has a syndiotacticity of usually 75% or more andpreferably 85% or more based on racemic diads or a syndiotacticity ofusually 30% or more and preferably 50% or more based on racemic pentads.

The polystyrene-based polymer having a syndiotactic structure includes ahomopolymer of styrene or a styrene derivative (when appropriate,styrene and styrene derivatives may be collectively referred tohereinbelow as “styrene compounds”) or a copolymer of any of styrenecompounds with an optional monomer. As the polymer, one type thereof maybe solely used, or two or more types thereof may be used in combination.Examples of the styrene derivatives may include a styrene derivativehaving a substituent on the benzene ring or at an α position of styrene.Examples of the styrene compounds may include: styrene; alkyl styrenessuch as methylstyrene and 2,4-dimethylstyrene; halogenated styrenes suchas chlorostyrene; halogen-substituted alkyl styrenes such aschloromethylstyrene; and alkoxystyrenes such as methoxystyrene. As thestyrene or styrene derivative, one type thereof may be solely used, ortwo or more types thereof may be used in combination at any ratio.

Preferred examples of the optional monomer for use in thepolystyrene-based polymer having the syndiotactic structure may includeacrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. Inthe present invention, preferable ones of these are homopolymers ofstyrene or styrene derivatives from the viewpoint of high degree ofphase difference expression and compatibility with the polyaryleneether. Syndiotactic polystyrene, which is a homopolymer of styrene, isparticularly preferable. When the optional monomer is copolymerized, thepolymerization ratio of the optional monomer is preferably less than 5%by weight from the viewpoint of compatibility with the polyarylene etherresin.

The weight average molecular weight of the polystyrene-based polymerhaving the syndiotactic structure is usually 130,000 or more, preferably140,000 or more, and more preferably 150,000 or more and is usually300,000 or less, preferably 270,000 or less, and more preferably 250,000or less. When the weight average molecular weight is in such a range,the glass transition temperature of the polystyrene-based polymer can beraised, and the heat resistance of the phase difference film can therebybe stably improved.

The glass transition temperature of the polystyrene-based polymer havingthe syndiotactic structure is usually 85° C. or higher, preferably 90°C. or higher, and more preferably 95° C. or higher. By raising the glasstransition temperature of the polystyrene-based polymer as describedabove, the glass transition temperature of the resin composition (A) canbe effectively raised, and therefore the heat resistance of the phasedifference film can be stably improved. From the viewpoint of stable andeasy production of the phase difference film, the glass transitiontemperature of the polystyrene-based polymer having the syndiotacticstructure is usually 160° C. or lower, preferably 155° C. or lower, andmore preferably 150° C. or lower.

The polystyrene-based polymer having the syndiotactic structure may beproduced, e.g., by polymerization of any of the styrene compounds using,as catalysts, a titanium compound and a condensation product of waterand trialkylaluminium in an inert hydrocarbon solvent or in the absenceof a solvent (see Japanese Patent Application Laid-Open No. Sho.62-187708 A). Poly(halogenated alkylstyrene) may be produced, e.g., by amethod described in Japanese Patent Application Laid-Open No. Hei.1-146912 A.

The polyarylene ether is a polymer including a repeating unit having anarylene ether skeleton in its main chain. Particularly, a polymerincluding a phenylene ether unit represented by the following formula(I) is preferable as the polyarylene ether.

In the formula (I), each Q¹ independently represents a halogen atom, alower alkyl group (for example, an alkyl group having 7 or less carbonatoms), a phenyl group, a haloalkyl group, an aminoalkyl group, ahydrocarbon oxy group, or a halohydrocarbon oxy group (with a provisothat a halogen atom and an oxygen atom are separated by at least twocarbon atoms). Of these, as Q¹, an alkyl group and a phenyl group arepreferable, and an alkyl group having 1 or more and 4 or less carbonatoms is particularly preferable.

In the formula (I), each Q² independently represents a hydrogen atom, ahalogen atom, a lower alkyl group (for example, an alkyl group having 7or less carbon atoms), a phenyl group, a haloalkyl group, a hydrocarbonoxy group, or a halohydrocarbon oxy group (with a proviso that a halogenatom and an oxygen atom are separated by at least two carbon atoms). Ofthese, a hydrogen atom is preferable as Q².

The polyarylene ether may be a homopolymer having one type of structuralunit or a copolymer having two or more types of structural units.

When the polymer containing the structural unit represented by theformula (I) is a homopolymer, preferred examples of the homopolymer mayinclude a homopolymer having a 2,6-dimethyl-1,4-phenylene ether unit (arepeating unit represented by “—(C₆H₂(CH₃)₂—O)—”).

When the polymer containing the structural unit represented by theformula (I) is a copolymer, preferred examples of the copolymer mayinclude a random copolymer having a combination of a2,6-dimethyl-1,4-phenylene ether unit and a2,3,6-trimethyl-1,4-phenylene ether unit (i.e., a repeating unitrepresented by “—(C₆H(CH₃)₃—O—)—”).

The polyarylene ether may contain a repeating unit other than thearylene ether unit. In this case, the polyarylene ether is a copolymerhaving the arylene ether unit and a structural unit other than thearylene ether unit. However, it is preferable that the ratio of thestructural unit other than the arylene ether unit in the polyaryleneether is small to the extent that the effects of the present inventionare not significantly impaired. The ratio is usually 50% by weight orless, preferably 30% by weight or less, more preferably 20% by weight orless, and particularly preferably 0% by weight.

As the polyarylene ether, one type thereof may be solely used, or a twoor more types thereof may be used in combination at any ratio.

The ratio of the polystyrene-based polymer having a syndiotacticstructure with respect to the polyarylene ether in the resin composition(A), i.e., the weight ratio of (the polystyrene-based polymer having thesyndiotactic structure):(polyarylene ether), is 65:35 to 55:45,preferably 63.5:36.5 to 56.5:43.5, and more preferably 62:38 to 58:42.When the composition of the resin is within this range, a phasedifference film in which Re₄₅₀/Re₅₅₀ and Re₆₅₀/Re₅₅₀ are within desiredranges, which will be described later, can be easily obtained when thephase difference film is formed by stretching.

The resin composition (A) may contain a component other than thepolystyrene-based polymer having the syndiotactic structure and thepolyarylene ether, so long as the effects of the invention are notsignificantly impaired.

For example, the resin composition (A) may contain a polymer other thanthe polystyrene-based polymer having the syndiotactic structure and thepolyarylene ether. The amount of the polymer other than thepolystyrene-based polymer having the syndiotactic structure and thepolyarylene ether is preferably 15 parts by weight or less, morepreferably 10 parts by weight or less, still more preferably 5 parts byweight or less, and particularly preferably 0 parts by weight based on100 parts by weight of the total amount of the polystyrene-based polymerhaving the syndiotactic structure and the polyarylene ether.

The resin composition (A) may also contain, e.g., an additive. Examplesof the additive may include: lamellar crystal compounds; fine particles;stabilizers such as an antioxidant, a thermostabilizer, a lightstabilizer, a weathering stabilizer, an ultraviolet absorber, and a nearinfrared absorber; a plasticizer; coloring agents such as dyes and apigment; and an antistatic agent. As the additive, one type thereof maybe used, or two or more types thereof may be used in combination at anyratio. The amount of the additive may be appropriately set within therange in which the effects of the present invention are notsignificantly impaired. For example, the amount may be set within therange in which the total light transmittance of the phase differencefilm can be maintained at 85% or higher.

The glass transition temperature of the resin composition (A) is usually115° C. or higher, preferably 120° C. or higher, and more preferably125° C. or higher. Higher glass transition temperature of the resincomposition (A) brings about better heat resistance of the phasedifference film. However, excessively high glass transition temperaturemay hinder production of the phase difference film. Therefore, the glasstransition temperature of the resin composition (A) is usually 200° C.or lower.

(Phase Difference Film)

The phase difference film for use in the present invention satisfies therelation Re₄₅₀<Re₅₅₀<Re₆₅₀. Re₄₅₀, Re₅₅₀, and Re₆₅₀ representretardations in the in-plane direction of the phase difference film atmeasurement wavelengths of 450 nm, 550 nm, and 650 nm, respectively.This usually means that the phase difference film has inverse wavelengthdistribution property. When the phase difference film having suchinverse wavelength distribution property is applied to an organic ELdisplay device, changes in color tone at different observation anglescan be reduced, and effects such as correction of retardation can beobtained uniformly over a wide wavelength range.

Regarding the relationship of these parameters, Re₄₅₀/Re₅₅₀ ispreferably 0.95 or less, more preferably 0.90 or less, and still morepreferably 0.88 or less and is preferably 0.80 or more. Re₆₅₀/Re₅₅₀ ispreferably 1.05 or more and more preferably 1.10 or more and ispreferably 1.20 or less. When Re₄₅₀, Re₅₅₀, and Re₆₅₀ satisfy theserelations, the effects such as correction of retardation can be obtainedmore uniformly over a wide wavelength range.

Preferably, in the phase difference film according to the presentinvention, the in-plane direction retardation Re₅₅₀ at a measurementwavelength of 550 nm is 110 nm or more and 150 nm or less. By havingsuch retardation, the phase difference film can function as a ¼ waveplate, and a stacked product of the phase difference film and apolarizing film can act as a circularly polarizing plate.

The in-plane direction retardation at each measurement wavelength(Re₄₅₀, Re₅₅₀, and Re₆₅₀) is a value represented by |nx−ny|×d (whereinnx represents a refractive index in a direction of a slow axis in theplane of the phase difference film, ny represents a refractive index ina direction of a fast axis in the plane of the phase difference film,and d represents a film thickness).

The phase difference film for use in the present invention has abirefringence Δn at a wavelength of 550 nm of preferably 0.0020 or moreand more preferably 0.0030 or more. Δn is preferably 0.0050 or less andmore preferably 0.0045 or less. Herein Δn−nx−ny, and nx and ny are thesame as those described above. When Δn is within the aforementionedrange, the phase difference film can have reduced thickness, and changesin the optical properties of the phase difference film over the lapse oftime can be suppressed.

The phase difference film for use in the present invention has an Nzcoefficient at a wavelength of 550 nm of −0.25 to −0.05 and preferably−0.18 to −0.10. The Nz coefficient is a value represented by(nx−nz)/(nx−ny) (where nx and ny are the same as those described above,and nz represents a refractive index in the thickness direction of thephase difference film). A phase difference film having an Nz coefficientwithin the aforementioned range can be easily produced by diagonalstretching, and can realize good viewing angle characteristics of theorganic EL display device of the present invention.

Since the phase difference film is used as an optical film, the totallight transmittance of the phase difference film is preferably 85 ormore and more preferably 92% or more. The total light transmittance isan average value calculated from values measured at five points using a“turbidimeter NDH-300A” manufactured by NIPPON DENSHOKU INDUSTRIES Co.,Ltd. in accordance with JIS K7361-1997.

The haze of the phase difference film is preferably 1% or less, morepreferably 0.8% or less, and particularly preferably 0.5% or less. Whenthe haze value is small, the clarity of an image displayed on a displaydevice in which the phase difference film is installed can be increased.The haze is an average value calculated from values measured at fivepoints using a “turbidimeter NDH-300A” manufactured by NIPPON DENSHOKUINDUSTRIES Co., Ltd. in accordance with JIS K7361-1997.

The phase difference film for use in the present invention has a ΔYI ofpreferably 5 or less and more preferably 3 or less. When the ΔYI iswithin the aforementioned range, good visibility without coloring can beachieved. The ΔYI is determined as the arithmetic average ofmeasurements repeated five times using a “spectral color-differencemeter SE2000” manufactured by NIPPON DENSHOKU INDUSTRIES Co., Ltd. inaccordance with ASTM E313.

The thickness of the phase difference film is usually 5 μm or more,preferably 8 μm or more, more preferably 10 μm or more, and particularlypreferably 20 μm or more and is usually 500 μm or less, preferably 80 μmor less, and more preferably 50 μm or less.

(Additional Layer)

The phase difference film for use in the present invention may be a filmincluding only a layer formed of the resin composition (A).Alternatively, the phase difference film for use in the presentinvention may optionally include an additional layer other than thelayer formed of the resin composition (A), so long as the opticalfunction of the phase difference film is not inhibited. The phasedifference film prepared as a layered body including the layer formed ofthe resin composition (A) and the additional layer other than the layerformed of the resin composition (A) in this manner may be referred tohereinbelow as a “multi-layer phase difference film”. For example, themulti-layer phase difference film may include a transparent resin layerfor increasing the strength of the phase difference film. The materialconstituting the transparent resin layer may be any thermoplastic resin(B) that is capable of reinforcing the strength of the phase differencefilm. The thermoplastic resin (B) is more preferably one or moreselected from acrylic resins, resins containing alicyclicstructure-containing polymers, and polycarbonate resins and isparticularly preferably an acrylic resin or a resin containing analicyclic structure-containing polymer. From the viewpoint offacilitating co-stretching process with an unstretched film formed ofthe resin composition (A), the thermoplastic resin (B) is preferably aresin which does not express optical anisotropy under the stretchingconditions which will be described later.

The acrylic resin constituting the thermoplastic resin (B) is a resincontaining an acrylic polymer. The acrylic polymer means a polymer of(meth)acrylic acid or a derivative of (meth)acrylic acid. Examples ofthe acrylic polymer may include homopolymers and copolymers of acrylicacid, acrylic acid ester, acrylamide, acrylonitrile, methacrylic acid,methacrylic acid ester, etc. Since the acrylic resin is hard with highdurability, the acrylic resin layer can appropriately protect the layerformed of the resin composition (A), so that the strength of themulti-layer phase difference film can be increased.

The acrylic polymer is preferably a polymer containing a structural unitformed by polymerization of a (meth)acrylic acid ester. Examples of the(meth)acrylic acid ester may include alkyl esters of (meth)acrylic acid.Particularly, a (meth)acrylic acid ester having a structure derived from(meth)acrylic acid and an alkanol or cycloalkanoyl having 1 to 15 carbonatoms is preferable, and a (meth)acrylic acid ester having a structurederived from (meth)acrylic acid and an alkanol having 1 to 8 carbonatoms is more preferable.

Specific examples of the acrylic acid ester may include methyl acrylate,ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate,i-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexylacrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate,n-decyl acrylate, and n-dodecyl acrylate.

Specific examples of the methacrylic acid ester may include methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, i-propylmethacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butylmethacrylate, t-butyl methacrylate, n-hexyl methacrylate, n-octylmethacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, andn-dodecyl methacrylate.

The aforementioned (meth)acrylic acid ester may have a substituent suchas a hydroxyl group or a halogen atom within the range in which theeffects of the present invention are not significantly impaired.Examples of the (meth)acrylic acid ester having such a substituent mayinclude 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 4-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropylmethacrylate, and glycidyl methacrylate. One type thereof may be solelyused, or a two or more types thereof may be used in combination at anyratio.

The acrylic polymer may be a polymer of only (meth)acrylic acid or aderivative of (meth)acrylic acid or may be a copolymer of (meth)acrylicacid or a derivative of (meth)acrylic acid with a monomercopolymerizable therewith. Examples of the copolymerizable monomer mayinclude α,β-ethylenic unsaturated carboxylic acid ester monomers otherthan (meth)acrylic acid esters, α,β-ethylenic unsaturated carboxylicacid monomers, alkenyl aromatic monomers, conjugated diene monomers,non-conjugated diene monomers, esters of carboxylic acids andunsaturated alcohols, and olefin monomers. One type thereof may besolely used, or a two or more types thereof may be used in combinationat any ratio.

Further, as the acrylic polymer, one type thereof may be solely used, ora two or more types thereof may be used in combination at any ratio.

Among the aforementioned acrylic polymers, polymethacrylates arepreferable, and polymethyl methacrylate is more preferable.

The acrylic resin may contain rubber particles. When the acrylic resincontains the rubber particles, the flexibility of the acrylic resin canbe increased, and the shock resistance of the multi-layer phasedifference film can thereby be improved. In addition, the rubberparticles form irregularities on the surface of the acrylic resin layer,and the area of contact on the surface of the acrylic resin layer isreduced. Therefore, usually, slidability on the surface of the acrylicresin layer can be increased.

Examples of the rubber forming the rubber particles may include acrylicacid ester polymer rubbers, polymer rubbers composed mainly ofbutadiene, and ethylene-vinyl acetate copolymer rubbers. Examples of theacrylic acid ester polymer rubber may include rubbers containing butylacrylate, 2-ethylhexyl acrylate, etc. as a main component of the monomerunit. Of these, acrylic acid ester polymer rubbers containing butylacrylate as a main component and polymer rubbers containing butadiene asa main component are preferable.

The rubber particles may contain two or more types of rubbers. Theserubbers may be uniformly mixed or may be layered. Examples of the rubberparticles containing layered rubbers may include particles in which thelayers form a core-shell structure, wherein: the core is formed from arubber elastic component obtained by grafting an alkyl acrylate such asbutyl acrylate and styrene; and a hard resin layer (shell) is formedfrom a copolymer of an alkyl acrylate with one or both of polymethylmethacrylate and methyl methacrylate.

The number average particle diameter of the rubber particles ispreferably 0.05 μm or more and more preferably 0.1 μm or more and ispreferably 0.3 μm or less and more preferably 0.25 μm or less. When thenumber average particle diameter is within the aforementioned range,appropriate irregularities can be formed on the surface of the acrylicresin layer to improve the slidability of the multi-layer phasedifference film.

The amount of the rubber particles is preferably parts by weight or moreand preferably 50 parts by weight or less based on 100 parts by weightof the acrylic polymer. When the amount of the rubber particles iswithin the aforementioned range, the shock resistance of the multi-layerphase difference film can be increased to thereby improve itshandleability.

The acrylic resin may contain a component other than the acrylic polymerand the rubber particles, so long as the effects of the invention arenot significantly impaired. For example, the acrylic resin may contain apolymer other than the acrylic polymer. However, from the viewpoint ofexerting the advantages of the present invention to a significantdegree, it is preferable that the amount of the polymer other than theacrylic polymer and the rubber particles in the acrylic resin is small.For example, the specific amount of the polymer other than the acrylicpolymer and the rubber particles is preferably 10 parts by weight orless, more preferably 5 parts by weight or less, and still morepreferably 3 parts by weight or less based on 100 parts by weight of theacrylic polymer. Particularly preferably, the acrylic resin contains nopolymer other than the acrylic polymer and the rubber particles.

From the viewpoint of exerting the advantages of the present inventionto a significant degree, it is preferable that the amount of the polymerother than the acrylic polymer in the acrylic resin is small. Forexample, the specific amount of the polymer other than the acrylicpolymer is preferably 10 parts by weight or less, more preferably 5parts by weight or less, and still more preferably 3 parts by weight orless based on 100 parts by weight of the acrylic polymer. Particularlypreferably, the acrylic resin contains no polymer other than the acrylicpolymer.

The glass transition temperature of the acrylic resin is usually 80° C.or higher and preferably 90° C. or higher and is usually 120° C. orlower and preferably 110° C. or lower. When the glass transitiontemperature of the acrylic resin is equal to or higher than the lowerlimit in the aforementioned range, blocking of resin pellets duringdrying at high temperature can be suppressed, so that contamination ofthe resin pellets with water can be prevented. When the glass transitiontemperature of the acrylic resin is equal to or lower than the upperlimit, the degree of orientation of the acrylic polymer duringstretching can be reduced, so that inhibition of exertion of the opticalfunction by the layer formed of the resin composition (A) can besuppressed.

The glass transition temperature of the acrylic resin is preferablyequal to or lower than Tg_(A)−10° C. and more preferably equal to orlower than Tg_(A)−20° C., wherein Tg_(A) is the glass transitiontemperature of the resin composition (A). When the glass transitiontemperature of the acrylic resin is equal to or lower than the upperlimit in the aforementioned range, rupture of a P1 layer under thestretching temperature conditions which will be described later can beprevented, and a phase difference film having Δn, Re₅₅₀, and Re₄₅₀/Re₅₅₀within desired ranges can be easily obtained.

The alicyclic structure-containing polymer constituting thethermoplastic resin (B) is a polymer having an alicyclic structure inthe repeating unit of the polymer, and any of a polymer having analicyclic structure in its main chain and a polymer having an alicyclicstructure in a side chain may be used. As the alicyclicstructure-containing polymer, one type thereof may be solely used, or atwo or more types thereof may be used in combination at any ratio.Particularly, from the viewpoint of mechanical strength, heatresistance, etc., a polymer containing an alicyclic structure in itsmain chain is preferable.

Examples of the alicyclic structure may include saturated alicyclichydrocarbon (cycloalkane) structures and unsaturated alicyclichydrocarbon (cycloalkene or cycloalkyne) structures. Of these, thecycloalkane structures and cycloalkene structures are preferable fromthe viewpoint of mechanical strength, heat resistance, etc., and thecycloalkane structures are particularly preferable.

The number of carbon atoms constituting one alicyclic structure ispreferably 4 or more and more preferably 5 or more and is preferably 30or less, more preferably 20 or less, and particularly preferably 15 orless. The number of carbon atoms within the aforementioned range ispreferable because the mechanical strength, heat resistance, andmoldability into film are highly balanced.

The ratio of the repeating unit having the alicyclic structure in thealicyclic structure-containing polymer may be appropriately selected inaccordance with the application purpose. The ratio is preferably 55% byweight or more, more preferably 70% by weight or more, and particularlypreferably 90% by weight or more. It is preferable from the viewpoint ofheat resistance that the ratio of the repeating unit having thealicyclic structure in the alicyclic structure-containing polymer iswithin the aforementioned range.

Examples of the alicyclic structure-containing polymer may includenorbornene-based polymers, monocyclic olefin-based polymers, cyclicconjugated diene-based polymers, vinyl alicyclic hydrocarbon-basedpolymers, and hydrogenated products thereof. Of these, norbornene-basedpolymers are preferable because they have good moldability.

Examples of the norbornene-based polymers may include: a ring-openingpolymer of a monomer having a norbornene structure, a ring-openingcopolymer of a monomer having a norbornene structure with anotheroptional monomer, and hydrogenated products thereof; and an additionpolymer of a monomer having a norbornene structure, an additioncopolymer of a monomer having a norbornene structure with anotheroptional monomer, and hydrogenated products thereof. Of these, thehydrogenated products of the ring-opening (co)polymer of a monomerhaving a norbornene structure is particularly preferable from theviewpoint of moldability, heat resistance, low hygroscopicity, sizestability, light weight, etc. The term “(co)polymer” refers to a polymerand a copolymer.

Examples of the monomer having a norbornene structure may includebicyclo[2.2.1]hept-2-ene (trivial name: norbornene),tricyclo[4.3.0.1^(2,5)]deca-3,7-diene (trivial name: dicyclopentadiene),7,8-benzotricyclo[4.3.0.1^(2,5)]deca-3-ene (trivial name:methanotetrahydrofluorene),tetracyclo[4.4.0.1^(2,5).1^(3,10)]dodeca-3-ene (trivial name:tetracyclododecene), and derivatives of these compounds (for example,compounds having substituents on their rings). Examples of thesubstituents may include alkyl groups, alkylene groups, and polargroups. A plurality of substituents may be bonded to the ring, and thesesubstituents may be the same or different from each other. As themonomer having a norbornene structure, one type thereof may be solelyused, or a two or more types thereof may be used in combination at anyratio.

Examples of the optional monomer copolymerizable with the monomer havinga norbornene structure through ring-opening may include: monocyclicolefins such as cyclohexene, cycloheptene, and cyclooctene andderivatives thereof; and cyclic conjugated dienes such as cyclohexadieneand cycloheptadiene and derivatives thereof.

As the optional monomer copolymerizable with the monomer having anorbornene structure through ring-opening, one type thereof may besolely used, or a two or more types thereof may be used in combinationat any ratio.

The ring-opening polymer of the monomer having a norbornene structureand the ring-opening copolymer of the monomer having a norbornenestructure with an optional monomer copolymerizable therewith may beproduced, e.g., by polymerization or copolymerization of the monomer(s)in the presence of a known ring-opening polymerization catalyst.

Examples of the monomer addition-copolymerizable with the monomer havinga norbornene structure may include: α-olefins having 2 to 20 carbonatoms such as ethylene, propylene, and 1-butene and derivatives thereof;cycloolefins such as cyclobutene, cyclopentene, and cyclohexene, andderivatives thereof; and non-conjugated dienes such as 1,4-hexadiene,4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene. Of these, α-olefinsare preferable, and ethylene is more preferable. As the optional monomeraddition-copolymerizable with the monomer having a norbornene structure,one type thereof may be solely used, or a two or more types thereof maybe used in combination at any ratio.

The addition polymer of the monomer having a norbornene structure andthe addition copolymer of the monomer having a norbornene structure withan optional monomer copolymerizable therewith may be produced, e.g., bypolymerization or copolymerization of the monomer(s) in the presence ofa known addition polymerization catalyst.

Examples of the monocyclic olefin-based polymer may include additionpolymers of monocyclic olefin-based monomers such as cyclohexene,cycloheptene, and cyclooctene.

Examples of the cyclic conjugated diene-based polymer may include:polymers obtained by cyclization reaction of addition polymers ofconjugated diene-based monomers such as 1,3-butadiene, isoprene, andchloroprene; 1,2- and 1,4-addition polymers of cyclic conjugateddiene-based monomers such as cyclopentadiene and cyclohexadiene; andhydrogenated products thereof.

Examples of the vinyl alicyclic hydrocarbon polymers may include:polymers of vinyl alicyclic hydrocarbon-based monomers such asvinylcyclohexene and vinylcyclohexane and hydrogenated products thereof;hydrogenated products obtained by hydrogenating aromatic ring portionscontained in polymers prepared by polymerization of vinyl aromatichydrocarbon-based monomers such as styrene and α-methylstyrene; andaromatic ring hydrogenated products of copolymers, such as randomcopolymers and block copolymers, of vinyl alicyclic hydrocarbon-basedmonomers and vinyl aromatic hydrocarbon-based monomers with monomerscopolymerizable with these vinyl aromatic hydrocarbon-based monomers.Examples of the block copolymers may include diblock copolymers,triblock copolymers, and higher multi-block copolymers, and graded blockcopolymers.

The glass transition temperature of the alicyclic structure-containingpolymer is preferably 80° C. or higher and more preferably 90° C. orhigher and is preferably 150° C. or lower, more preferably 120° C. orlower, and still more preferably 110° C. or lower. If the glasstransition temperature is too low, durability at high temperature maydeteriorate. Although the polymer having excessively high glasstransition temperature may give high durability, usual stretchingprocess on such a polymer may be difficult.

The glass transition temperature of the alicyclic structure-containingpolymer is preferably equal to or lower than Tg_(A)−10° C. and morepreferably equal to or lower than Tg_(A)−20° C., wherein Tg_(A) is theglass transition temperature of the resin composition (A). When theglass transition temperature of the alicyclic structure-containingpolymer is equal to or lower than the upper limit in the aforementionedrange, rupture of the P1 layer under the stretching temperatureconditions described later can be prevented, and a phase difference filmwith Δn, Re₅₅₀, and Re₄₅₀/Re₅₅₀ within desired ranges can be easilyobtained.

The polycarbonate resin constituting the thermoplastic resin (B) is aresin containing a polycarbonate polymer. As the polycarbonate polymer,any polymer may be used so long as it has a repeating unit including acarbonate bond (—O—C(═O)—O—).

Particularly, the polycarbonate polymer is preferably a polycarbonatepolymer containing a repeating unit A derived from bisphenol Z andrepresented by the chemical formula (II) below. Specific examples of theresin containing such a polycarbonate polymer may include LEXANmanufactured by SABIC.

In the chemical formula (II), R1 to R8 are each independently a hydrogenatom, a halogen atom, or an alkyl group, cycloalkyl group or aryl groupthat is substituted or unsubstituted and has 1 to 10 carbon atoms. R9 isa hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an arylgroup. Z is a residue forming a saturated or unsaturated carbon ringhaving 4 to 11 carbon atoms together with carbon atoms to which theresidue is bonded. The carbon ring is preferably a saturated carbon ringhaving 6 carbon atoms. R1 (or R3) is preferably an alkyl group having 1to 10 carbon atoms and more preferably a methyl group. R6 (or R8) ispreferably an alkyl group having 1 to 10 carbon atoms and morepreferably a methyl group. The repeating unit A represented by thechemical formula (II) above is preferably a repeating unit representedby the chemical formula (III).

Preferably, the polycarbonate polymer further contains, in addition tothe repeating unit A, a repeating unit B derived from bisphenol A andrepresented by the chemical formula (IV) below. Particularly preferably,the repeating unit B is a repeating unit represented by the chemicalformula (V). In the combination of the repeating unit A and therepeating unit B, it is preferable that the amount of the repeating unitB represented by the chemical formula (IV) is 0.6 moles or more and 1.5moles or less based on 1 mole of the repeating unit A represented by thechemical formula (II). When the composition of the polycarbonate polymeris within the aforementioned preferable range, a resin which expresseslow degree of optical anisotropy during stretching can be formed.

In the chemical formula (IV), R₁₀ to R₁₇ are each independently ahydrogen atom, a halogen atom, or an alkyl group, cycloalkyl group oraryl group that is substituted or unsubstituted and has 1 to 10 carbonatoms.

The glass transition temperature Tg of the polycarbonate resin isusually 80° C. or higher, preferably 90° C. or higher, more preferably100° C. or higher, and particularly preferably 120° C. or higher and ispreferably 160° C. or lower and more preferably 150° C. or lower. If theglass transition temperature is too low, durability at high temperaturemay deteriorate. Although the resin having excessively high glasstransition temperature may give high durability, usual stretchingprocess on such a resin may be difficult.

The thermoplastic resin (B) may contain, e.g., an additive. Examples ofthe additive may include the same additives as those that may becontained in the resin composition (A). As the additive, one typethereof may be solely used, or a two or more types thereof may be usedin combination at any ratio. The amount of the additive may beappropriately set within the range in which the effects of the presentinvention are not significantly impaired.

(Method for Producing Phase Difference Film)

The phase difference film for use in the present invention includes alayer formed of the aforementioned resin composition (A). Usually, theresin composition (A) is molded to produce a long-length pre-stretchfilm, and the obtained pre-stretch film is subjected to stretchingtreatment to thereby obtain a phase difference film. A “long-length”film is a film having a length at least 5 times longer than its widthand preferably 10 times longer than the width and is more specifically afilm having a length that allows the film to be wound to be in a rollform for storage or conveyance. In a production line of such along-length film, the long-length film is obtained by performingproduction steps continuously in the lengthwise direction of the film.Therefore, upon production of the phase difference film, part of or allthe steps can be simply and efficiently performed in-line.

As the method for producing the pre-stretch film, e.g., a flow castingmethod may be used. However, melt extrusion molding is preferable fromthe viewpoint of production efficiency and from the viewpoint ofavoiding existence of the residual volatile components such as a solventin the film. The melt extrusion molding may be performed using, e.g., aT-die method.

The thickness of the pre-stretch film is preferably 10 μm or more andmore preferably 120 μm or more and is preferably 800 μm or less and morepreferably 200 μm or less. When the thickness is equal to or more thanthe lower limit in the aforementioned range, sufficient retardation andmechanical strength can be obtained. When the thickness is equal to orless than the upper limit in the aforementioned range, favorableflexibility and handleability can be obtained.

By stretching the obtained pre-stretch film, the film expressesretardation, and a phase difference film is thereby obtained. In thiscase, the expressed retardation has inverse wavelength distributionproperty. The mechanism of the expression of inverse wavelengthdistribution property is deduced to be as follows.

Usually, in the visible wavelength range of 400 nm to 700 nm, thewavelength distribution property of the polyarylene ether having apositive intrinsic birefringence value is higher than the wavelengthdistribution property of the polystyrene-based polymer having thesyndiotactic structure and having a negative intrinsic birefringencevalue. In the resin composition (A) in the present invention, e.g., theformulation and other factors of the polyarylene ether and thepolystyrene-based polymer having the syndiotactic structure are adjustedsuch that the influence by the orientation of the polystyrene-basedpolymer having the syndiotactic structure is slightly larger than theinfluence by the orientation of the polyarylene ether on theshort-wavelength side, and such that the influence by the orientation ofthe polystyrene-based polymer having the syndiotactic structure appearsmore remarkably as the wavelength approaches toward the long-wavelengthside.

The retardation expressed after the pre-stretch film is stretched isusually the difference between the retardation expressed by theorientation of the polyarylene ether contained in the resin composition(A) in the present invention and the retardation expressed by theorientation of the polystyrene-based polymer having the syndiotacticstructure. Therefore, when the adjustment is effected such that theinfluence of the polystyrene-based polymer having the syndiotacticstructure appears more remarkably as the wavelength approaches towardthe long-wavelength side as described above, a phase difference filmhaving inverse wavelength distribution property can be obtained.

The stretching operation to be employed may be; a method in whichuniaxial stretching is performed in the lengthwise direction byutilizing the difference in peripheral speed between rolls (longitudinaluniaxial stretching); a method in which uniaxial stretching is performedin the width direction using a tenter (crosswise uniaxial stretching); amethod in which longitudinal uniaxial stretching and crosswise uniaxialstretching are performed sequentially (sequential biaxial stretching);or a method in which stretching is performed in a diagonal directionwith respect to the lengthwise direction of the pre-stretch film(diagonal stretching). Particularly, diagonal stretching is preferablyused because the diagonal stretching usually gives a long-length phasedifference film having a slow axis in a diagonal direction, which inturn can reduce waste upon cutting rectangular products out of thelong-length phase difference film and can realize efficient productionof the phase difference film having a large surface area. The “diagonaldirection” means a direction that is non-parallel, non-orthogonaldirection.

Specific examples of the method for diagonal stretching may include astretching method using a tenter stretching machine. Examples of thetenter stretching machine may include a tenter stretching machine thatcan apply feeding force, tensile force, or drawing force with differentspeeds to the left and right edges of the pre-stretch film (i.e., theleft and right width-end edges of the pre-stretch film when the filmconveyed horizontally is observed in the MD direction). Another exampleis a tenter stretching machine which can achieve diagonal stretching byapplying feeding force, tensile force, or drawing force in the TD or MDdirection with the same speed to the left and right edges, and by havingnon-linear left and right tracks with the same moving distance. Stillanother example is a tenter stretching machine in which the left andright edges are moved at different distances to achieve diagonalstretching.

When stretching is performed in a diagonal direction, it is preferableto perform stretching in such a direction that the angle of thestretching direction with respect to the lengthwise direction of thepre-stretch film is 40° or more and 50° or less. In this manner, a phasedifference film having an orientation angle within the range of 40° ormore and 50° or less with respect to the lengthwise direction can beobtained. The “orientation angle” is the angle between the MD directionof the long-length phase difference film and the in-plane slow axis ofthe phase difference film.

When the phase difference film is used as a rectangular film piece, itis preferable that the film piece has a slow axis within the range of40° or more and 50° or less with respect to the direction of the edge ofthe rectangular shape. In such a case, when the orientation angle iswithin the range of 40° or more and 50° or less with respect to thelengthwise direction, the rectangular film product can be cut out fromthe long-length phase difference film simply by cutting out therectangular film piece with its edges being in the direction parallel toor orthogonal to the lengthwise direction, whereby efficient productioncan be performed and area size can be easily enlarged.

The temperature of the film during stretching is preferably equal to orhigher than Tg_(A)−20° C., more preferably equal to or higher thanTg_(A)−15° C., and still more preferably equal to or higher thanTg_(A)−13° C., wherein Tg_(A) is the glass transition temperature of theresin composition (A). The temperature of the film during stretching ispreferably equal to or lower than Tg_(A)+20° C., more preferably equalto or lower than Tg_(A)+2° C., still more preferably equal to or lowerthan Tg_(A)+1° C., yet more preferably equal to or lower than Tg_(A)−2°C., and particularly preferably equal to or lower than Tg_(A)−11° C.

The stretching ratio is preferably 1.2 to 6 times and more preferably2.5 to 5.0 times. When the stretching ratio is within this range, a thinphase difference film that satisfies the relation Re₄₅₀<Re₅₅₀<Re₆₅₀ andhas Re₅₅₀ within a desired range can be easily obtained. The number ofstretching operations may be one or may be two or more.

When the phase difference film is produced, a step other than thosedescribed above may be performed. For example, the pre-stretch film maybe subjected to pre-heat treatment before stretching.

In the aforementioned method for producing the phase difference film,the long-length pre-stretch film may be a long-length pre-stretch filmlayered body, including a P1 layer formed of the resin composition (A)and a P2 layer formed of the thermoplastic resin (B). The pre-stretchfilm layered body may include only one P2 layer but preferably includestwo or more P2 layers. Particularly preferred examples of thepre-stretch film layered body may include a pre-stretch film layeredbody including a first P2 layer, a P1 layer, and a second P2 layer inthis order. In such a pre-stretch film layered body, the P1 layer can beprotected by the high-strength P2 layers that sandwich the P1 layer fromopposite sides, so that bleedout from the P1 layer can be effectivelyprevented. The bleedout from the P1 layer is a phenomenon in which partof the components (for example, an additive) contained in the P1 layerbleeds out through the surface of the P1 layer.

Examples of the method for producing the pre-stretch film layered bodymay include: co-extrusion molding methods such as a co-extrusion T-diemethod, a co-extrusion inflation method, and a co-extrusion laminationmethod; film lamination forming methods such as dry lamination; aco-flow casting method; and a coating forming method in which thesurface of a resin film is coated with a resin solution. Of these,co-extrusion molding methods are preferable from the viewpoint ofproduction efficiency and of avoiding existence of the residual volatilecomponent such as a solvent in the pre-stretch film layered body.

When the co-extrusion molding method is used, the pre-stretch filmlayered body may be obtained by, e.g., co-extrusion of the resincomposition (A) and the thermoplastic resin (B). Examples of theco-extrusion molding method may include a co-extrusion T-die method, aco-extrusion inflation method, and a co-extrusion lamination method. Ofthese, the co-extrusion T-die method is preferable. Examples of theco-extrusion T-die method may include a feed block procedure and amulti-manifold procedure. The multi-manifold procedure is particularlypreferable because thickness variations can thereby be reduced.

When the co-extrusion T-die method is used, the temperature for meltingthe resins in an extruder having a T-die is set to a temperature higherthan the glass transition temperatures of the resin composition (A) andthe thermoplastic resin (B) by preferably 80° C. or more and morepreferably 100° C. or more and by preferably 180° C. or less and morepreferably 150° C. or less. By setting the melting temperature in theextruder to be equal to or higher than the lower limit in theaforementioned range, the flowability of the resins can be sufficientlyincreased. By setting the melting temperature to be equal to or lowerthan the upper limit, deterioration of the resins can be prevented.

By stretching the pre-stretch film layered body, a phase difference filmlayered body is obtained which includes a layer formed by the stretchingof the P1 layer formed of the resin composition (A) (this layer may bereferred to hereinbelow as a “p1 layer”) and a layer formed by thestretching of the P2 layer formed of the thermoplastic resin (B) (thislayer may be referred to hereinbelow as a “p2 layer”). As the stretchingmethod, any of the aforementioned methods may be used.

When the phase difference film layered body as its entirety satisfiesthe relation Re₄₅₀<Re₅₅₀<Re₆₅₀ and has an Nz coefficient of −0.25 to−0.05 at a wavelength of 550 nm, the phase difference film layered bodyas it is may be used as the phase difference film for the organic ELdisplay device of the present invention. In this case, from theviewpoint of effectively utilizing the phase difference expressed in thep1 layer to obtain desired optical properties, it is preferable that theabsolute value of the phase difference expressed by stretching in the p2layer is small, and it is more preferable that no phase difference isexpressed in the p2 layer. More specifically, in-plane directionretardation in the p2 layer is more than 1 nm and less than 10 nm.

In this case, the stretching temperature of the pre-stretch film ispreferably higher than Tg_(B) by 10° C. or more and more preferablyhigher than Tg_(B) by 20° C. to 60° C., wherein Tg_(B) is the glasstransition temperature of the thermoplastic resin (B). The stretchingratio in this case is preferably 1.1 to 6 times. When stretching isperformed under such conditions, rupture of the P1 layer duringstretching can be prevented, and the in-plane direction retardation ofthe p2 layer can be adjusted within the aforementioned range.

Alternatively, a phase difference film may be obtained by removing thep2 layer from the phase difference film layered body. In this case, itis not necessary to take the phase difference expressed in the p2 layerinto consideration. Therefore, the thickness of the P2 layer in thepre-stretch film layered body and the stretching conditions may be setsuch that desired optical properties are expressed in the p1 layer. Whenthe p2 layer is removed, it is preferable, from the viewpoint of theease of removal, to use an acrylic resin or an alicyclicstructure-containing polymer as the thermoplastic resin (B). Thespecific range of the thickness of the P2 layer in the pre-stretch filmlayered body is preferably equal to or more than 0.3 times the thicknessof the P1 layer, more preferably equal to or more than 0.5 times, stillmore preferably equal to or more than 1.0 times, and particularlypreferably equal to or more than 2.0 times and is preferably equal to orless than 5.0 times and more preferably equal to or less than 3.0 times.When the pre-stretch film layered body has a plurality of P2 layers, itis preferable that each single layer has a thickness within theaforementioned range.

Particularly preferably, a phase difference film is obtained by:stretching a pre-stretch film layered body including a first P2 layer, aP1 layer, and a second P2 layer in this order to obtain a phasedifference film layered body including a first p2 layer, a p1 layer, anda second p2 layer in this order; and removing the first and second p2layers from the phase difference film layered body. With this method,the P1 layer can be protected by the high-strength P2 layers thatsandwich the P1 layer from opposite sides, rupture of the P1 layer canbe prevented, and stretching at a high stretching ratio can beperformed. Stretching performed at a high stretching ratio brings aboutexpression of large phase difference by the orientation of the resincomposition (A), so that thickness of the p1 layer can be reduced. Sincethe p2 layers are removed, the thickness of the obtained phasedifference film can be reduced, and a reduction in thickness of theorganic EL display device of the present invention can be achieved.

(Hard-Coat Layer)

It is preferable that the aforementioned phase difference film has ahard-coat layer on one or more of its surfaces. The phase differencefilm may have a hard-coat layer only on one surface or may havehard-coat layers on both surfaces. Preferably, the phase difference filmhas a hard-coat layer at least on a surface opposite to the surface onthe side on which the polarizing film is stacked. When the phasedifference film has a hard-coat layer, the anti-reflection effect andstrength of the circularly polarizing plate can be further improved.

The hard-coat layer is a layer for reinforcing the hardness of aprotective film and preferably has a hardness of “H” or higher asmeasured by a pencil hardness test (a glass plate is used as a testplate) in accordance with JIS K5600-5-4. Preferably, the phasedifference film having such a hard-coat layer has a pencil hardness of4H or higher. The material for forming the hard-coat layer (a hard-coatmaterial) is preferably a thermosetting or photocurable material, andexamples of such a material may include: organic hard-coat materialssuch as organic silicone-based, melamine-based, epoxy-based,acrylic-based, and urethane acrylate-based materials; and inorganichard-coat materials such as silicon dioxide. Of these, urethaneacrylate-based and polyfunctional acrylate-based hard-coat materials arepreferably used as the hard-coat material because of their high adhesionand good productivity.

No limitation is imposed on the thickness of the hard-coat layer. Thethickness is appropriately determined and is preferably 1 μm to 20 μmand more preferably 3 μm to 10 μm.

If necessary, the hard-coat layer may contain a variety of fillers, inorder to adjust the refractive index of the hard-coat layer, improve itsbending elastic modulus, stabilize its volumetric shrinkage rate, and toimprove its heat resistance, antistatic properties, antiglareproperties, etc. The hard-coat layer may further contain additives suchas an antioxidant, an ultraviolet absorber, a light stabilizer, anantistatic agent, a leveling agent, and an antifoaming agent.

Examples of the filler for adjusting the refractive index and antistaticproperties of the hard-coat layer may include titanium oxide, zirconiumoxide, zinc oxide, tin oxide, cerium oxide, antimony pentoxide,tin-doped indium oxide (ITO), antimony-doped tin oxide (IZO),aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO). Thefiller is preferably antimony pentoxide, ITO, IZO, ATO, or FTO formaintaining transparency. The primary particle diameter of the filler isusually 1 nm to 100 nm and preferably 1 nm to 30 nm.

As the filler for imparting antiglare properties, those having anaverage particle diameter of 0.5 μm to 10 μm are preferable. Thosehaving an average particle diameter of 1.0 μm to 7.0 μm are morepreferable, those having an average particle diameter of 1.0 μm to 4.0μm are still more preferable. Specific examples of the filler forimparting antiglare properties may include: fillers formed of organicresins such as polymethyl methacrylate resins, vinylidene fluorideresins, other fluorine resins, silicone resins, epoxy resins, nylonresins, polystyrene resins, phenolic resins, polyurethane resins,cross-linked acrylic resins, cross-linked polystyrene resins, melamineresins, and benzoguanamine resins; and fillers formed of inorganiccompounds such as titanium oxide, aluminum oxide, indium oxide, zincoxide, antimony oxide, tin oxide, zirconium oxide, ITO, magnesiumfluoride, and silicon oxide.

The refractive index of the hard-coat layer is preferably 1.57 to 1.61.When the refractive index of the hard-coat layer is within theaforementioned range, a good anti-reflection effect is obtained.

The phase difference film for use in the present invention may furtherinclude an optional layer such as a mat layer for improving theslidability of the film, an anti-reflection layer, or an anti-foulinglayer.

(Polarizing Film)

The circularly polarizing plate for use in the present invention isformed by stacking a polarizing film and the aforementioned phasedifference film. Specifically, the polarizing film and the phasedifference film are stacked such that the angle between the slow axis ofthe phase difference film and the absorption axis of the polarizing filmis within the range of 40° or more and 50° or less.

The polarizing film for stacking is preferably a long-length polarizingfilm having an absorption axis in its lengthwise direction. This isbecause the direction of the slow axis of the phase difference film andthe direction of the absorption axis of the polarizing plate can therebybe set to appropriate angles by simply stacking the long-length phasedifference film and the long-length polarizing film with theirlongitudinal axis directions aligned with each other, and thisfacilitates production of the circularly polarizing plate.

The long-length polarizing film may be produced by, e.g., causing iodineor a dichromatic dye to be adsorbed onto a polyvinyl alcohol film andthen uniaxially stretching the resultant film in a boric acid bath. Thelong-length polarizing film may also be produced, e.g., by causingiodine or a dichromatic dye to be adsorbed onto a polyvinyl alcoholfilm, stretching the resultant film, and then modifying part of thepolyvinyl alcohol units in the molecular chain into polyvinylene units.Further, as the polarizing film, a polarizing film having a function ofseparating polarized light into reflected light and transmitted light,such as a grid polarizing plate or a multi-layer polarizing plate mayalso be used. Of these, a polarizing film containing polyvinyl alcoholis preferable. The degree of polarization of the polarizing film ispreferably 98% or more and more preferably 99% or more. The thickness(average thickness) of the polarizing film is preferably 5 μm to 80 μm.

Upon stacking the polarizing film and the phase difference film, anadhesive may be used. No particular limitation is imposed on theadhesive so long as it is optically transparent. Examples of theadhesive may include water-based adhesives, solvent-type adhesives,two-component curing adhesives, ultraviolet curable adhesives, andpressure sensitive adhesives. Of these, water-based adhesives arepreferable, and polyvinyl alcohol-based water-based adhesives areparticularly preferable. As the adhesive, one type thereof may be solelyused, or a two or more types thereof may be used in combination at anyratio.

The average thickness of the layer formed of the adhesive (adhesivelayer) is preferably 0.05 μm or more and more preferably 0.1 μm or moreand is preferably 5 μm or less and more preferably 1 μm or less.

No limitation is imposed on the method for stacking the phase differencefilm on the polarizing film. A preferred method includes applying theadhesive to one surface of the polarizing film, laminating thepolarizing film and the phase difference film using a roll laminator,and then drying the laminate. Before lamination, the surface of thephase difference film may be subjected to surface treatment such ascorona discharge treatment or plasma treatment. The drying time anddrying temperature may be appropriately selected in accordance with thetype of adhesive.

If necessary, the obtained circularly polarizing plate is cut into anappropriate size, to be used as an anti-reflection film for the organicEL display device of the present invention. An organic EL display devicehaving favorable visibility even in the presence of external light canbe provided by disposing such an anti-reflection film on thelight-emitting side of the organic EL display device with the phasedifference film disposed toward the light-emitting layer of the organicEL display device.

(Substrate)

No particular limitation is imposed on the substrate for use in theorganic EL display device of the present invention, so long as thesubstrate is transparent. The thickness of the substrate is usuallyabout 50 μm to about 2.0 mm. Examples of the material used for thesubstrate may include glass materials, resin materials, and compositematerials thereof. Examples of the composite materials may include aglass plate with a plastic protective film or layer provided thereon.

Examples of the resin materials and the material of the protectiveplastic may include fluorine resins, polyethylene, polypropylene,polyvinyl chloride, polyvinyl fluoride, polystyrenes, ABS resins,polyamides, polyacetals, polyesters, polycarbonates, modifiedpolyphenylene ethers, polysulfones, polyarylates, polyetherimides,polyamide-imides, polyimides, polyphenylene sulfides, liquid crystallinepolyesters, polyethylene terephthalates, polybutylene terephthalates,polyethylene naphthalates, polyoxymethylenes, polyethersulfones,polyether ether ketones, polyacrylates, acrylonitrile-styrene resins,phenolic resins, urea resins, melamine resins, unsaturated polyesterresins, epoxy resins, polyurethanes, silicone resins, and amorphouspolyolefin. Other resin materials can also be used so long as thematerials are polymer materials that may be used for the organic ELdisplay device.

Although it depends on the application of the organic EL display device,it is more preferable that the substrate has high gas barrier propertiesagainst water vapor, oxygen, etc. A gas barrier layer for preventingtransmission of water vapor, oxygen, etc. may be formed on thesubstrate. For example, the gas barrier layer is preferably a layer ofan inorganic oxide such as silicon oxide, aluminum oxide, or titaniumoxide formed by a physical vapor deposition method such as a sputteringmethod or a vacuum vapor deposition method.

(Transparent Electrode)

The transparent electrode is usually used as a positive electrode andforms an electrode wiring pattern together with signal lines and scanlines formed on the substrate and TFTs (thin-film transistors) servingas driving elements. No particular limitation is imposed on the materialof the transparent electrode so long as it is a material used forgeneral organic EL display devices, and metals, alloys, mixturesthereof, etc. may be used. Specific examples of the material of thetransparent electrode may include thin-film electrode materials such asindium tin oxide (ITO), indium oxide, indium zinc oxide (IZO), zincoxide, stannic oxide, and gold. Preferably, the transparent electrode isformed of a transparent material having a large work function (4 eV orhigher), such as ITO, IZO, indium oxide, or gold, for facilitating holeinjection. The sheet resistance of the transparent electrode ispreferably several hundred ohms/square or less, and its thickness is,e.g., about 0.005 μm to about 1 μm, although the thickness may depend onthe material.

(Luminescent Layer)

No particular limitation is imposed on the luminescent layer of theluminescent element so long as the light-emitting layer is usually usedfor organic EL display devices, and any of low-molecular and polymerlight-emitting layers may be used. For example, the luminescent layermay have a structure in which a hole injection layer, the luminescentlayer, and an electron induction layer are formed in this order from thetransparent electrode layer side, a structure including only theluminescent layer, a structure including a hole injection layer and theluminescent layer, a structure including the luminescent layer and anelectron induction layer, a structure in which a hole transport layer isinterposed between a hole injection layer and the luminescent layer, ora structure in which an electron transport layer is interposed betweenthe luminescent layer and an electron induction layer. Each of thematerials of the aforementioned layers may be doped with a suitablematerial for adjusting the wavelength of light luminescence and forimproving the luminescence efficiency.

(Metal Electrode Layer)

The metal electrode layer is usually used as a negative electrode. Noparticular limitation is imposed on the material of the metal electrodelayer, so long as it is a material used for general organic EL displaydevices. Examples of the material may include gold, magnesium alloys(such as MgAg), aluminum, aluminum alloys (such as AlLi, AlCa, andAlMg), and silver. Preferably, the metal electrode layer is formed of amagnesium alloy, aluminum, silver, etc. having a small work function (4eV or lower), for facilitating electron injection. The sheet resistanceof the metal electrode layer is preferably several hundred ohms/squareor less, and therefore its thickness is preferably, e.g., about 0.005 μmto about 0.5 μm.

EXAMPLES

The present invention will be specifically described by way of Examples.However, the present invention is not limited to the following Examples.The present invention may be implemented with any modifications withoutdeparting the scope of the claims of the present invention andequivalents thereto. Unless otherwise specified, “part” and “%” In theExamples and Comparative Examples are based on weight. “Mw” represents aweight average molecular weight.

In the Examples and Comparative Examples, respective properties weremeasured as follows.

(Film Thicknesses)

The thicknesses of the respective layers of a film and the overallthickness of the film were measured as follows. The film was embedded inan epoxy resin and sliced using a microtome (“RUB-2100” manufactured byYAMATO KOHKI INDUSTRIAL Co., Ltd.), and the cross-section was observedunder a scanning electron microscope for measurement.

[Retardation, Nz Coefficient, and Birefringence]

The surface of a phase difference film was polished with an abrasivecloth for plastics to obtain each layer as a single layer. For eachsingle layer, a refractive index nx in the direction of a slow axis ofthe layer, a refractive index ny in an in-plane direction orthogonal tothe slow axis of the layer, and a refractive index nz in a thicknessdirection were measured at measurement wavelengths of 450 nm, 550 nm,and 650 nm using a spectroscopic ellipsometer M-2000U manufactured by J.A. Woollam. The retardation Re of each layer at each wavelength, its Nzcoefficient at a wavelength of 550 nm, and its birefringence Δn at awavelength of 550 nm were calculated from the aforementioned values andthickness d (nm) of the each layer in accordance with the followingformulas.Re=|nx−ny|×dNz=(nx−nz)/(nx−ny)Δn=nx−ny

[Glass Transition Temperature]

Measurement was performed using a differential scanning calorimeter(“EXSTAP6220” manufactured by Seiko Instruments Inc.) at a temperatureincrease rate of 20° C./min.

[Strength (Flexibility)]

Whether or not rupture occurred when a long-length phase difference filmand a long-length polarizer were continuously laminated was evaluated inaccordance with the following criteria.

A: No rupture occurred during lamination from feeding, and the filmswere capable to be laminated over their entire length.

B: Rupture occurred several times during lamination from feeding.

(Viewing Angle Characteristics of Organic EL Display Device)

As to a model in which a reflecting plate and a circularly polarizingplate were stacked such that the phase difference film of the circularlypolarizing plate was in contact with the reflecting plate, opticalsimulations with a 4×4 matrix were performed to calculate contrast andcolor tone, and the results were displayed as a contrast map and a colortone map (a diagram representing color shifts). In the contrast map,darker color is indicative of higher contrast. In the color tone map,lighter color is indicative of larger color shift.

The circularly polarizing plate was disposed on a glass substrate of anorganic EL display device such that the phase difference film was incontact with the glass substrate. The display characteristics when thedisplay device was observed obliquely in upward, downward, left, andright directions were visually checked and judged in accordance with thefollowing criteria.

A: No reflection of an external scenery and no change in color tone werefound.

B: A slight reflection of an external scenery and a slight change incolor tone were found.

C: A small reflection of an external scenery and a small change in colortone were found.

D: A significant reflection of an external scenery and a significantchange in color tone were found.

Example 1 Production of Pre-Stretch Film

58 Parts of syndiotactic polystyrene (“XAREC 130ZC” manufactured byIdemitsu Kosan Co., Ltd., Mw: 180,000), 42 parts ofpoly(2,6-dimetyl-1,4-phenylene oxide) (catalog No. 18242-7, ALDRICH),and 1 part of an antioxidant were kneaded in a twin screw extruder toproduce pellets of a transparent resin composition (A). The glasstransition temperature of the resin composition (A) was 134° C.

As the thermoplastic resin (B), pellets of an acrylic resin (“HT55Z”manufactured by Sumitomo Chemical Co., Ltd., glass transitiontemperature: 108° C.) containing an acrylic polymer and rubber particleswere fed to one of the single screw extruders of a film formingapparatus, and melted.

The pellets of the aforementioned resin composition (A) were fed toanother one of the single screw extruders of the film forming apparatus,and melted.

A film forming apparatus for two-type three-layer co-extrusion moldingwas prepared, and the melted thermoplastic resin (B) was passed througha polymer filter having a leaf disc shape and an opening of 10 μm andthen supplied to one of manifolds of a multi-manifold die (surfaceroughness of a die lip: Ra=0.1 μm) of the film forming apparatus.

The melted resin composition (A) was passed through a polymer filterhaving a leaf disc shape and an opening of 10 μm, and then supplied toanother one of the manifolds of the film forming apparatus.

The thermoplastic resin (B) and the resin composition (A) weresimultaneously extruded from the multi-manifold die at 260° C. while theextrusion conditions were controlled so that resin layers with desiredthicknesses were obtained, whereby the resins were formed into a filmshape having a three-layer structure of (a P2 layer formed of thethermoplastic resin (B))/(a P1 layer formed of the resin composition(A))/(a P2 layer formed of the thermoplastic resin (B)). The meltedresins co-extruded into a film shape were casted onto a cooling rollerhaving a surface temperature adjusted to 115° C. and then passed betweentwo cooling rollers having a surface temperature adjusted to 120° C. Inthis manner, a pre-stretch film layered body of a three-layer structurehaving the P2 layer, the P1 layer, and the P2 layer in this order wasobtained (co-extrusion step). The ratio of the thicknesses of theselayers was P2 layer:P1 layer:P2 layer=2:1:2.

(Production of Stretched Film)

Subsequently, this pre-stretch film layered body was diagonallystretched using a tenter stretching machine such that the slow axis wasinclined at an angle of 45° with respect to the MD direction. Thetemperature during stretching was set to 131° C., which was atemperature lower than the glass transition temperature of the resincomposition (A) by 3° C., and the stretching ratio was set to 3.2 times.A phase difference film layered body having a three-layer structure of(a p2 layer formed of the thermoplastic resin (B))/(a p1 layer formed ofthe resin composition (A))/(a p2 layer formed of the thermoplastic resin(B)) was thereby obtained. The ratio of the thicknesses of these layerswas p2 layer:p1 layer:p2 layer=2:1:2. Subsequently, the p2 layers onboth sides were removed from the phase difference film layered body toobtain a long-length 49 μm-thick phase difference film A consisting onlyof the p1 layer. The obtained phase difference film A was wound to forma film roll. The orientation of the phase difference film A was checked,and the slow axis was found to be inclined at an angle of 45° withrespect to the MD direction. The Re₅₅₀ of the phase difference film Awas 140 nm. The phase difference film A satisfied the relationRe₄₅₀<Re₅₅₀<Re₆₅₀, and Re₄₅₀/Re₅₅₀ was 0.87. Δn was 0.0028, and the Nzcoefficient was −0.12.

(Production of Circularly Polarizing Plate)

A long-length 80 μm-thick polyvinyl alcohol film was stained in a 0.3%aqueous iodine solution. Then the resultant film was stretched at aratio of 5 times in a 4% aqueous boric acid solution and a 21 aqueouspotassium iodide solution and dried at 50° C. for 4 minutes to produce along-length polarizer.

The phase difference film A was continuously fed from the roll, andlaminated onto one surface of the long-length polarizer with a rolllaminator using an adhesive. During lamination from feeding, no ruptureoccurred, and the films were capable to be laminated over their entirelength. From the laminated films, a rectangular shape piece was cut outto produce a circularly polarizing plate A.

Using a model in which this circularly polarizing plate A was used,optical simulations with a 4×4 matrix were performed to calculatecontrast and color tone, and the results were displayed as a contrastmap and a color tone map. The results are shown in FIGS. 1 and 2. Inaddition, the circularly polarizing plate A was applied to an organic ELdisplay device, and viewing angle characteristics from upward, downward,left, and right directions were visually checked. The results are shownin Table 1.

Example 2

Pellets of transparent resin composition (A) were prepared in the samemanner as in Example 1 except that the amount of syndiotacticpolystyrene was changed to 57 parts and the amount ofpoly(2,6-dimetyl-1,4-phenylene oxide) was changed to 43 parts. The glasstransition temperature of the resin composition (A) was 136° C. Apre-stretch film layered body of a three-layer structure having a P2layer, a P1 layer, and a P2 layer in this order was obtained in the samemanner as in Example 1 except that the resin composition (A) thusproduced was used (co-extrusion step). The ratio of the thicknesses ofthese layers was P2 layer:P1 layer:P2 layer=3:1:3.

Subsequently, this pre-stretch film layered body was diagonallystretched using a tenter stretching machine at a stretching ratio of 2.8times such that the slow axis was inclined at an angle of 45° withrespect to the MD direction. The temperature during stretching was setto 121° C., which was a temperature lower than the glass transitiontemperature of the resin composition (A) by 15° C. A phase differencefilm layered body having a three-layer structure of (a p2 layer formedof the thermoplastic resin (B))/(a p1 layer formed of the resincomposition (A))/(a p2 layer formed of the thermoplastic resin (B)) wasthereby obtained. The ratio of the thicknesses of these layers was p2layer:p1 layer:p2 layer=3:1:3. Subsequently, the p2 layers on both sideswere removed from the phase difference film layered body to obtain along-length 35 μm-thick phase difference film B consisting only of thep1 layer. The obtained phase difference film B was wound to form a filmroll. The orientation of the phase difference film B was checked, andthe slow axis was found to be inclined at an angle of 45′ with respectto the MD direction. The Re₅₅₀ of the phase difference film B was 141nm. The phase difference film B satisfied the relationRe₄₅₀<Re₅₅₀<Re₆₅₀, and Re₄₅₀/Re₅₅₀ was 0.88. Δn was 0.0040, and the Nzcoefficient was −0.14.

Using the aforementioned phase difference film B, a circularlypolarizing plate B was produced in the same manner as in Example 1.During lamination from feeding from the roll, no rupture occurred in thephase difference film B, and the films were capable to be laminated overtheir entire length. Using the obtained circularly polarizing plate B,contrast and color tone were calculated, and viewing anglecharacteristics of an organic EL display device was evaluated. Theresults are shown in FIGS. 3 and 4 and Table 1.

Example 3

Pellets of transparent resin composition (A) were prepared in the samemanner as in Example 1 except that the amount of syndiotacticpolystyrene was changed to 64 parts and the amount ofpoly(2,6-dimetyl-1,4-phenylene oxide) was changed to 36 parts. The glasstransition temperature of the resin composition (A) was 127° C. Apre-stretch film layered body having a three-layer structure of a P2layer, a P1 layer, and a P2 layer in this order was obtained in the samemanner as in Example 1 except that the resin composition (A) thusprepared was used as the resin composition (A), and that pellets of aresin (“ZEONOR1060” manufactured by ZEON CORPORATION, glass transitiontemperature: 100° C.) containing an alicyclic structure-containingpolymer were used as the thermoplastic resin (B) (co-extrusion step).The ratio of the thicknesses of these layers was P2 layer:P1 layer:P2layer=1:1:1.

Subsequently, this pre-stretch film layered body was subjected tolongitudinal uniaxial stretching using a tenter stretching machine at astretching ratio of 1.4 times in the MD direction and then subjected todiagonal stretching at a stretching ratio of 1.6 times such that theslow axis was inclined at an angle of 45° with respect to the MDdirection. The temperatures during stretching, i.e., the temperatureduring longitudinal uniaxial stretching and the temperature duringdiagonal stretching, were set to 129° C., which was a temperature higherthan the glass transition temperature of the resin composition (A) by 2°C. A phase difference film layered body having a three-layer structureof (a p2 layer formed of the thermoplastic resin (B))/(a p1 layer formedof the resin composition (A))/(a p2 layer formed of the thermoplasticresin (B)) was thereby obtained. The ratio of the thicknesses of theselayers was p2 layer:p1 layer:p2 layer=1:1:1. Subsequently, the p2 layerson both sides were removed from the phase difference film layered bodyto obtain a long-length 99 μm-thick phase difference film C consistingonly of the p1 layer. The obtained phase difference film C was wound toform a film roll. The orientation of the phase difference film C waschecked, and the slow axis was found to be inclined at an angle of 45°with respect to the MD direction. The Re₅₅₀ of the phase difference filmC was 139 nm. The phase difference film C satisfied the relationRe₄₅₀<Re₅₅₀<Re₆₅₀, and Re₄₅₀/Re₅₅₀ was 0.96. Δn was 0.0014, and the Nzcoefficient was −0.22.

Using the aforementioned phase difference film C, an attempt was made toproduce a circularly polarizing plate in the same manner as inExample 1. However, rupture in the phase difference film C occurredseveral times during lamination from feeding from the roll.

Separately from this operation, a rectangular shape piece was cut outfrom the phase difference film C. A long-length polarizer was producedin the same manner as in Example 1 and therefrom a rectangular shapepiece was cut out. The cut-out phase difference film C was laminatedonto one surface of the cut-out polarizer with a roll laminator using anadhesive such that the angle between the slow axis of the phasedifference film C and the stretching direction of the polarizer was 45°to thereby produce a circularly polarizing plate C. Using thiscircularly polarizing plate C, contrast and color tone were calculated,and viewing angle characteristics of an organic EL display device wasevaluated. The results are shown in FIGS. 5 and 6 and Table 1.

Comparative Example 1

Pellets of transparent resin composition (A′) were produced in the samemanner as in Example 1 except that 57 parts of amorphous polystyrene(“HH102” manufactured by PS Japan Corporation, glass transitiontemperature: 101° C.) was used in place of 59 parts of syndiotacticpolystyrene and that the amount of poly(2,6-dimetyl-1,4-phenylene oxide)was changed to 43 parts. The glass transition temperature of the resincomposition (A′) was 141° C. A pre-stretch film layered body of athree-layer structure having a P2 layer formed of the thermoplasticresin (B), a P1′ layer formed of the resin composition (A′), and a P2layer formed of the thermoplastic resin (B) in this order was obtainedin the same manner as in Example 1 except that the pellets of the resincomposition (A′) were used in place of the pellets of the resincomposition (A) (co-extrusion step). The ratio of the thicknesses ofthese layers was P2 layer:P1′ layer:P2 layer=2:1:2.

Subsequently, this pre-stretch film layered body was diagonallystretched using a tenter stretching machine such that the slow axis wasinclined at an angle of 45° with respect to the MD direction. Thetemperature during stretching was set to 143° C., which was atemperature higher than the glass transition temperature of the resincomposition (A′) by 2° C., and the stretching ratio was set to 3.0times. A phase difference film layered body having a three-layerstructure of (a p2 layer formed of the thermoplastic resin (B))/(a p1′layer formed of the resin composition (A′))/(a p2 layer formed of thethermoplastic resin (B)) was thereby obtained. The ratio of thethicknesses of these layers was p2 layer:p1′ layer:p2 layer=2:1:2.Subsequently, the p2 layers on both sides were removed from the phasedifference film layered body to obtain a long-length 99 μm-thick phasedifference film D consisting only of the p1′ layer. The obtained phasedifference film D was wound to form a film roll. The orientation of thephase difference film D was checked, and the slow axis was found to beinclined at an angle of 45′ with respect to the MD direction. The Re₅₅₀of the phase difference film D was 138 nm. However the relationRe₄₅₀<Re₅₅₀<Re₆₅₀ was not satisfied. The Nz coefficient was +1.12.

Using the aforementioned phase difference film D, an attempt was made toproduce a circularly polarizing plate in the same manner as inExample 1. However, rupture occurred in the phase difference film Dseveral times during lamination from feeding from the roll.

Separately from this operation, a rectangular shape piece was cut outfrom the phase difference film D. A long-length polarizer was producedin the same manner as in Example 1 and therefrom a rectangular shapepiece was cut out. The cut-out phase difference film D was laminatedonto one surface of the cut-out polarizer with a roll laminator using anadhesive to thereby produce a circularly polarizing plate D. Using thiscircularly polarizing plate D, contrast and color tone was calculated,and viewing angle characteristics of an organic EL display device wasevaluated. The results are shown in FIGS. 7 and 8 and Table 1.

Comparative Example 2

Pellets of transparent resin composition (A) were produced in the samemanner as in Example 1 except that the amount of syndiotacticpolystyrene was changed to 63 parts and that the amount ofpoly(2,6-dimetyl-1,4-phenylene oxide) was changed to 37 parts. The glasstransition temperature of the resin composition (A) was 129° C. Thepellets of the resin composition (A) were melted using a single screwextruder, and supplied to an extrusion die, to performextrusion-molding, whereby a pre-stretch film was obtained. The obtainedpre-stretch film was subjected to simultaneous biaxial stretching in theMD and TD directions using a tenter stretching machine. The temperatureduring stretching was set to 132° C., which was a temperature higherthan the glass transition temperature of the resin composition (A) by 3°C. The stretching ratio was 1.3 times in the MD direction and 1.2 timesin the TD direction. A long-length 62 μm-thick phase difference film Ewas thereby obtained. The obtained phase difference film E was wound toform a film roll. The orientation of the phase difference film E waschecked, and the slow axis was found to be perpendicular to the MDdirection. The Re₅₅₀ of the phase difference film E was 142 nm. Thephase difference film E satisfied the relation Re₄₅₀<Re₅₅₀<Re₆₅₀, andRe₄₅₀/Re₅₅₀ was 0.95. Δn was 0.0023, and the Nz coefficient was −1.00.

Using this phase difference film E, an attempt was made to produce acircularly polarizing plate in the same manner as in Example 1. Duringlamination from feeding from the roll, no rupture occurred in the phasedifference film E, and the films were capable to be laminated over theirentire length.

Separately from this operation, a rectangular shape piece was cut outfrom the phase difference film e. A long-length polarizer was producedin the same manner as in Example 1 and therefrom a rectangular shapepiece was cut out. The cut-out phase difference film E was laminatedonto one surface of the cut-out polarizer with a roll laminator using anadhesive such that the angle between the slow axis of the phasedifference film E and the stretching direction of the polarizer was 45°to thereby produce a circularly polarizing plate E. Using thiscircularly polarizing plate E, contrast and color tone were calculated,and viewing angle characteristics of an organic EL display device wasevaluated. The results are shown in FIGS. 9 and 10 and Table 1.

Comparative Example 3

Pellets of transparent resin composition (A) were produced in the samemanner as in Example 1 except that the amount of syndiotacticpolystyrene was changed to 76 parts and the amount ofpoly(2,6-dimetyl-1,4-phenylene oxide) was changed to 24 parts. The glasstransition temperature of the resin composition (A) was 115° C. Thepellets of the resin composition (A) were melted using a single screwextruder, and supplied to an extrusion die, to performextrusion-molding, whereby a pre-stretch film having a thickness of 100μm was obtained.

Subsequently, an attempt was made to diagonally stretch the pre-stretchfilm using a tenter stretching machine in a direction inclined at anangle of 45° with respect to the MD direction. The temperature duringstretching was set to 103° C., which was a temperature lower than theglass transition temperature of the resin composition (A) by 12° C.However, the film was ruptured when the stretching ratio reached 1.5times, so that a phase difference film could not be obtained.

Comparative Example 4

A cellulose ester film (product name “KA” manufactured by KanekaCorporation) was diagonally stretched to obtain a long-length 100μm-thick phase difference film F. The obtained phase difference film Fwas wound to form a film roll. The orientation of the phase differencefilm F was checked, and the slow axis was found to be inclined at anangle of 45° with respect to the ND direction. The Re₅₅₀ of the phasedifference film F was 140 nm. The phase difference film F satisfied therelation Re₄₅₀<Re₅₅₀<Re₆₅₀, and the Nz coefficient was +1.13.

A circularly polarizing plate F was produced using this phase differencefilm F in the same manner as in Example 1. During lamination fromfeeding from the roll, no rupture occurred in the phase difference filmF, and the films were capable to be laminated over their entire length.Using the obtained circularly polarizing plate F, contrast and colortone were calculated, and viewing angle characteristics of an organic ELdisplay device was evaluated. The results are shown in FIGS. 11 and 12and Table 1.

TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Comp. Ex. 2 Ex. 3 Ex.4 Phase difference film A B C D E — F Resin Syndiotactic 58 57 64 — 6376 — composition polystyrene (parts) Amorphous — — — 57 — — —polystyrene Polyarylene ether 42 43 36 43 37 24 — Cellulose ester — — —— — — 100 Manner of stretching Diagonal Diagonal Longi- Diagonal Longi-Diagonal Diagonal (stretching ratio) (3.2) (2.8) tudunal (2.5) tudinal(1.3) + (1.5) (1.4) + diagonal diagonal (1.2) (1.6) simultaneoussequential Stretching temperature (° C.) Tg−3 Tg−12 Tg+2 Tg+2 Tg+3 Tg−12— Film thickness (μm) 49 35 99 99 62 Phase — Re₅₅₀ 138 141 139 138 142difference 138 Re₄₅₀ < Re₅₅₀ < Re₆₅₀ OK OK OK NG OK film OK Re₄₅₀/Re₅₅₀0.87 0.88 0.96 — 0.95 not — Birefringence Δn 0.0028 0.0040 0.0014 —0.0023 obtainable — Nz coefficient −0.12 −0.14 −0.22 +1.12 −1.00 +1.12Strength (flexibility) A A B B A A Viewing angle characteristics A A B DD D

As is clear from the aforementioned Examples and Comparative Examples,the organic EL devices of the present invention have high contrast,small color shifts, and good viewing angle characteristics. However, theorganic EL devices in the Comparative Examples have low contrast, largecolor shifts, and poor viewing angle characteristics.

The invention claimed is:
 1. An organic EL display device comprising asubstrate, a transparent electrode, a luminescent layer, and a metalelectrode layer in this order from a light emission side, the organic ELdisplay device further comprising a circularly polarizing plate disposedon the light emission side of the substrate, the circularly polarizingplate including a polarizing film and a phase difference film that arestacked on each other, wherein the phase difference film includes alayer formed of a resin composition (A) containing a polystyrene-basedpolymer having a syndiotactic structure and polyarylene ether, a ratioof the polystyrene-based polymer having the syndiotactic structure withrespect to the polyarylene ether in the resin composition (A) is 65:35to 55:45, the ratio being a weight ratio of (the polystyrene-basedpolymer having the syndiotactic structure) with respect to (thepolyarylene ether), the phase difference film satisfies a relationRe₄₅₀<Re₅₅₀<Re₆₅₀, and an Nz coefficient of the phase difference film ata wavelength of 550 nm is −0.25 to −0.05 (wherein Re₄₅₀, Re₅₅₀, andRe₆₅₀ are in-plane direction retardations of the phase difference filmat measurement wavelengths of 450 nm, 550 nm, and 650 nm, respectively,the Nz coefficient represents (nx−nz)/(nx−ny), nx represents arefractive index in a direction of an in-plane slow axis of the phasedifference film, ny represents a refractive index in a direction of anin-plane fast axis of the phase difference film, and nz represents arefractive index in a thickness direction of the phase difference film).2. The organic EL display device according to claim 1, whereinRe₄₅₀/Re₅₅₀ in the phase difference film is 0.80 or more and 0.90 orless.
 3. The organic EL display device according to claim 1, wherein abirefringence Δn (Δn=nx−ny) of the phase difference film at a wavelengthof 550 nm is 0.0020 or more and 0.0050 or less.
 4. The organic ELdisplay device according to claim 1, wherein the phase difference filmhas a thickness of 80 μm or less.
 5. The organic EL display deviceaccording to claim 1, wherein the polyarylene ether contains a polymerincluding a phenylene ether unit.
 6. The organic EL display deviceaccording to claim 1, wherein the in-plane direction retardation Re₅₅₀of the phase difference film at a measurement wavelength of 550 nm is110 nm to 150 nm.
 7. The organic EL display device according to claim 1,wherein the phase difference film is prepared by subjecting along-length pre-stretch film formed of the resin composition (A) tostretching in a direction within a range of 40° or more and 50° or lesswith respect to a lengthwise direction of the long-length pre-stretchfilm.
 8. The organic EL display device according to claim 7, wherein thestretching is performed at a temperature equal to or higher than(Tg−15)° C. and equal to or lower than (Tg+1)° C., wherein (Tg) is theglass transition temperature of the resin composition (A).
 9. Theorganic EL display device according to claim 1, wherein the phasedifference film is prepared by subjecting a long-length pre-stretch filmlayered body to stretching in a direction within a range of 40° or moreand 50° or less with respect to a lengthwise direction of thelong-length pre-stretch film layered body, the pre-stretch film layeredbody including a P1 layer formed of the resin composition (A) and a P2layer provided in contact with the P1 layer and formed of athermoplastic resin (B).
 10. The organic EL display device according toclaim 9, wherein the thermoplastic resin (B) is at least one selectedfrom acrylic resins, resins containing alicyclic structure-containingpolymers, and polycarbonate resins.
 11. The organic EL display deviceaccording to claim 10, wherein the long-length pre-stretch film layeredbody is obtained by co-extrusion or co-flow casting of the resincomposition (A) and the thermoplastic resin (B).
 12. The organic ELdisplay device according to claim 9, wherein the long-length pre-stretchfilm layered body is obtained by co-extrusion or co-flow casting of theresin composition (A) and the thermoplastic resin (B).
 13. The organicEL display device according to claim 9, wherein the stretching isperformed at a temperature equal to or higher than (Tg−15)° C. and equalto or lower than (Tg+1)° C., wherein (Tg) is the glass transitiontemperature of the resin composition (A).
 14. The organic EL displaydevice according to claim 1, wherein the phase difference film isprepared by: subjecting a long-length pre-stretch film layered body tostretching in a direction within a range of 40° or more and 50° or lesswith respect to a lengthwise direction of the long-length pre-stretchfilm layered body, the pre-stretch film layered body including a P1layer formed of the resin composition (A) and a P2 layer provided incontact with the P1 layer and formed of a thermoplastic resin (B),whereby a phase difference film layered body including a p1 layer formedby stretching the P1 layer and a p2 layer formed by stretching the P2layer is obtained; and then removing the p2 layer.
 15. The organic ELdisplay device according to claim 14, wherein the thermoplastic resin(B) is at least one selected from acrylic resins, resins containingalicyclic structure-containing polymers, and polycarbonate resins. 16.The organic EL display device according to claim 14, wherein thelong-length pre-stretch film layered body is obtained by co-extrusion orco-flow casting of the resin composition (A) and the thermoplastic resin(B).
 17. The organic EL display device according to claim 14, whereinthe stretching is performed at a temperature equal to or higher than(Tg−15)° C. and equal to or lower than (Tg+1)° C., wherein (Tg) is theglass transition temperature of the resin composition (A).